Jewish journalists covering the presidential race have seen a surge in anti-semitic tweets since Donald Trump entered the presidential race, according to a report by the Anti-Defamation League (ADL).

In the report released Wednesday, the organization found that 2.6 million anti-Semitic messages were posted on Twitter from August 2015 to July 2016. Of those, 19,253 were directed at journalists.

When voters started casting ballots in the primary contests and the presidential campaign began to intensify, the report saw a significant increase in hateful tweets. More than 800 journalists have been the subject of anti-Semitic attacks on Twitter, with 10 of them receiving 83 percent of the total attacks.

While the report was careful not to say Trump caused the trend of targeting journalists, it suggested “he may have created an atmosphere in which such targeting arose.” “We cannot conclude that Mr. Trump’s extensive use of Twitter ‘encouraged’ these attacks,” the report continued. “Mr. Trump’s use of Twitter as a key communications tool is notable, but the platform is used extensively by all candidates.”

In several instances along the presidential race, the report found spikes in anti-Semitic Twitter activity. On Feb. 29, 2016, during peak coverage of Trump’s refusal to “disavow” the Ku Klux Klan, the organization saw a huge rise in anti-Semitic tweets directed at journalists.

The report names specific journalists who received the brunt of harassment. Bethany Mandel, a freelance reporter who wrote critically about Trump, said one user tweeted hateful messages about her for 19 consecutive hours. She received messages containing images with her face superimposed on photos of Nazi concentration camps. Ben Shapiro, a conservative political commentator and originator of the #NeverTrump movement, told ADL: “When my child was born there were lots of anti-Semitic responses talking about cockroaches.”

The report said the aggressors identified as Trump supporters, conservatives, or part of the “alt-right," a loosely connected group of extremists, some of whom are white supremacists. They found the words that appear most frequently in the 1,600 Twitter attackers’ bios were “Trump,” “nationalist,” “conservative,” and “white.”

While most of the aggressors remained anonymous, two accounts were identified as noted white supremacists: Andrew Anglin, founder of the popular white supremacist web site “The Daily Stormer” and Lee Rogers of Infostormer. Both are banned from Twitter, but have encouraged their followers to tweet anti-Semitic language and memes at Jewish journalists.

Trump has not responded to the report but on Wednesday criticized a liberal media bias on his Twitter account.